Automatic calibration of a network analyzer

Abstract

A radio frequency network analyzer connected to a multi-port test set is calibrated. An initial calibration is performed for each test set port in the multi-port test set. The initial calibration is performed by first performing a measurement calibration using calibration standards. The calibration standards are located in a reference plane located outside the multi-port test set. The measurement calibration yields initial calibration coefficients. Also the initial calibration includes measuring electronic standards within the multi-port test set to produce initial measured electronic standards. The initial calibration coefficients and the measured electronic standards are used to generate initial corrected electronic standards.

I claim: 
     
       1. A method for performing calibration of a network analyzer system, the method comprising the following steps: (a) performing an initial calibration for test ports of the network analyzer system comprising the following substeps: (a.1) performing a measurement calibration using calibration standards, the calibration standards being located in a reference plane located outside the network analyzer system, the measurement calibration yielding initial calibration coefficients,   (a.2) measuring electronic standards within the network analyzer system to produce initial measured electronic standards, and   (a.3) using the initial calibration coefficients and the measured electronic standards to generate initial corrected electronic standards; and,     (b) performing an automatic recalibration for the test ports, the automatic recalibration being performed after initial calibration of all the test ports in step (a), the automatic recalibration being performed without use of calibration standards located in a reference plane located outside the network analyzer system and the automatic recalibration comprising the following substeps: (b.1) measuring the electronic standards within the network analyzer system to produce recalibration measured electronic standards, and   (b.2) using the recalibration measured electronic standards and the initial corrected electronic standards to produce recalculated calibration coefficients.     
     
     
       2. A method as in claim 1 wherein in substep (a.2) the electronic standards approximate an open, a short and a load. 
     
     
       3. A method as in claim 1 wherein in substep (a.1) the initial calibration coefficients comprise: three reflection error coefficients: directivity (DIR), source match (SM) and reflection tracking (RT); and,   one transmission error coefficient: transmission tracking (TT).   
     
     
       4. A method as in claim 3 wherein in substep (a.1) measured values (R --  RAW) for reflection calibration standards are related to corrected values (R --  COR) for the reflection calibration standards in accordance with an equation as set out below: ##EQU12## 
     
     
       5. A method as in claim 3 wherein in substep (a.1) a measured value (T --  RAW) for a transmission calibration standard is related to a corrected value (T --  COR) for the transmission calibration standard in accordance with an equation as set out below: 
     
     
       6. A method as in claim 3 wherein in substep (a.3) the initial corrected electronic standards include reflection calibration standards and measured values (R --  RAW) for the reflection calibration standards are related to corrected values (R --  COR) for the reflection calibration standards in accordance with an equation as set out below: 
     
     
       7. A method as in claim 3 wherein in substep (a.3) the initial corrected electronic standards include a transmission calibration standard and a measured value (T --  RAW) for the transmission calibration standard is related to a corrected value (T --  COR) for the transmission calibration standard in accordance with an equation as set out below: 
     
     
       8. A method as in claim 1 wherein the network analyzer system includes a network analyzer connected to multi-port test set and the test ports of the network analyzer system are test set ports of the multi-port test set. 
     
     
       9. A method as in claim 8 wherein the test set ports are divided into pairs and substep (a.1) includes the following substep used to generate transmission coefficients for each pair of test set ports: (a.1.1) determining a first ratio of transmission response of fixtures and cables to calibration through transmission response, wherein the calibration through transmission response is determined using a calibration through line to electrically connect each pair of test set ports and the transmission response of the fixtures and the cables is determined using the fixtures and the cables to electrically connect together each pair of test set ports. 
     
     
       10. A method as in claim 9 wherein when calculating a transmission response error coefficient between a first test set port and a second test set port where the second test set port is paired with a third test set port: substep (b.1) includes measuring transmission response of an internal calibration through path transmission value between the third test set port and the second test set port; and,   substep (b.2) includes multiplying the transmission response of the internal calibration through path transmission value between the third test set port and the second test set port measured in substep (b.1) by the first ratio calculated in substep (a.1.1) for the internal calibration through path transmission value between the third test set port and the second test set port and by a second ratio, the second ratio being the transmission response between a reflection input of the multi-port test set and the first port to the transmission response between the reflection input of the multi-port test set and the third port.